When conventional electric wiring is replaced with optical wiring, in addition to an optical transmission medium, various components such as a laser diode (LD) for converting an electrical signal into an optical signal, a driver integrated circuit (IC), an optical waveguide for transmitting an optical signal, a photodiode (PD) for converting a detected optical signal back into an electrical signal, and a receiver integrated circuit (IC) are required. In recent years, a vertical-cavity surface-emitting laser (VCSEL) for emitting light through its surface has been widely used as the laser diode (LD). The vertical-cavity surface-emitting laser has the advantages that a two-dimensional array can be manufactured, a circular symmetrical beam cross-section can be obtained, and power consumption can be reduced. In addition, the vertical-cavity surface-emitting laser can inspect whether a device on a wafer operates properly before cutting a chip, and can make more devices per unit area to thereby reduce manufacturing costs. An optical fiber and a dielectric optical waveguide are widely used as the optical waveguide for transmitting an optical signal. A PIN photodiode (PD) is widely used as a photodetector. A Si-based circuit such as a Si CMOS or SiGe BiCMOS circuit is widely used as the driver IC and the receiver IC in order to reduce manufacturing costs.
In general, in order to transmit light through the optical wiring, the optical fiber or the dielectric optical waveguide is used. In the optical wiring integrated module, an optical signal is transmitted through an optical waveguide made of a dielectric material such as glass, silica, polymer, or the like. In addition, in order to obtain a compact and integrated module, a built-in optical waveguide is used in various optical printed circuit boards (PCBs). Though a multi-mode optical waveguide is mainly used to increase optical alignment efficiency and readily manufacture an optical PCB module, it is difficult to manufacture a relatively large built-in optical waveguide and thus its yield is quite low.
In addition, most optical PCBs used nowadays use the vertical-cavity surface-emitting laser. The vertical-cavity surface-emitting laser or the photodiode is mounted on the surface of a substrate. In this case, since the vertical-cavity surface-emitting laser or the photodiode vertically emits or receives light, in order to connect the light to the optical waveguide horizontally mounted on the optical PCB, a connector component for changing a light path by 90° is required. Different types of connector components, such as a 45° mirror formed at an end part of the optical waveguide and a 90° bent optical waveguide block, have been developed and are currently used. However, there is still no secure solution, and thus new technology needs to be developed.